The present invention relates to thin, crisp sliced fruit or vegetable snacks and a unique method of making them.
A number of methods for drying fruit or vegetable chips have been proposed to provide ready-to-eat snack foods. However, all of the methods proposed for making such sweetened food products to date have involved a soaking or steeping step wherein the freshly cut fruit or vegetable slices must be immersed in a sugar solution for a substantial period of time. While this process results in acceptable food products, such a soaking step has at least four serious drawbacks: because the slices must be soaked for from three minutes to two or more hours, this step severely limits the production rate and increases capital requirements to produce such products in commercial quantities. Secondly, when such chip-type raw materials are placed in a solution for soaking, they inevitably overlie one another so that when they are removed from the immersion tank, there are often two or more layers of slices presented to the drying ovens, resulting in inadequate or uneven drying and therefore unacceptable finished products. Thirdly, by immersing the slices in the sugar solution, the contact surface between the slice and the conveyor belt which moves the slice downstream for further processing is sticky, causing adhesion of the slice to the belt and resulting in difficult removal of the slice from the belt, as well as potentially uneven drying of the slice. Lastly, it has been found that the immersion of fruit or vegetable slices in the sugar solution causes a reduced flavor perception by the consumer, which can be shown analytically in gas-liquid chromatography flavor profiles.
It has been widely known, but for the most part ignored by producers of prepared fruit products, that the consumers of such products may be broadly classified in two distinct categories: those that prefer (consciously or subconsciously) sweet-tasting fruit or vegetable products, and those that likewise prefer tart-tasting fruit or vegetable products.
U.S. Pat. No. 3,365,309, Pader, et al, describes a process wherein prepared unblanched fruit is immersed in an aqueous crystallizing sugar solution for from forty five minutes to twenty two hours and then dried for up to sixteen hours. Another process is described in U.S. Pat. No. 3,962,355, Yamazaki, et al, wherein apple pieces are soaked in a 30-40 percent sugar solution for about fifteen to twenty minutes and subsequently dried. U.S. Pat. No. 3,833,747, Cordling, et al, discloses a process wherein apple segments were soaked in a 40 percent sucrose solution for two hours, and thereafter drained and dried. Numerous other processes have been described for making fruit chips, all of which apparently rely upon relatively long sucrose solution soak times in order to impregnate the fruit slices with sufficient quantities of sweetner to make the desired end product.
However, applicant has found that sliced fruit or vegetable pieces, when immersed in sucrose solutions for the amount of time suggested by the processes noted above, became extremely limp and were essentially impossible to work with thereafter. When soaked for the periods of time noted above, the slices lose most of their structural integrity due to a phenomenon known as osmotic dehydration (see, for example, Ponting, et al, Osmotic Dehydration of Fruits, Food Technol. Vol. 20 p. 125). Osmotic transfer of the water in the sliced fruit or vegetable from within the cellular structure to the surrounding sucrose solution renders the sliced products an essentially unworkable mass, much in the same way that a paper tissue loses its shape and integrity when immersed in water. Because the food slices become limp, when they are removed from the sucrose solution bath, it is virtually impossible to "monolayer" the slices without expensive monolayering equipment, such as that described in co-pending application, Ser. No. 512,979, commonly assigned with this application. As a result of this processing defect, Ser. No. 484,488 commonly assigned, disclosed a process whereby the fruit slices were steeped in a sucrose solution for from three to ten minutes, with approximately five minutes being preferred. While this appeared to be the lower limit of residence time in a sucrose solution bath, such period of time is still a rate-limiting factor for a commercial scale production operation. Additionally, there is still a significant level of osmotic dehydration, with associated difficulties in monolayering, when such a process is used. Therefore, there is a critical need for a process whereby fruit or vegetable chips may be prepared in a commercially feasible process not limited by time, capital, or processing restraints.